Monolithic microwave integrated circuits (MMICs) designed to operate at microwave frequencies are typically manufactured on top of single semiconductor substrates. As is generally the case with integrated circuits, placing the circuit components on a single substrate saves space. From an electronic standpoint, integrated circuits help reduce or eliminate problems such as parasitic capacitance loss that can arise when discrete devices are wire-bonded to one another to form circuits. These advantages can help integrated circuits operate at improved bandwidths as compared to circuits that are “wired” together from discrete components.
The growth of technologies dependent on MMICs will require that devices become smaller, more powerful and easier to manufacture. These desired advantages apply to base, relay and switching stations as well as to end user devices such as cellular telephones or other portable electronic devices. Due in part to the expansion of devices using MMICs, there may exist an increased need to raise operating voltages within the devices. In many applications MMIC capacitors are needed to work in the 140 volt (140 V) range and this figure is expected to increase significantly over the next several years. However, increasing operating voltages results in problems with AC and DC corona effects due at least in part to relatively high electric fields, notably in the space between the high voltage side of the capacitor and the nearest ground. These high voltage levels and the circuit features around such voltages result in electric field strengths sufficient to generate partial discharge and the onset of corona. Corona often cause catastrophic failure of the MMIC. Increasing the space between components will not offer solutions to most corona occurrences since corona induced failures are not caused by the spacing between the high voltage side of the capacitor and the ground via.
Alternative techniques and mechanisms for corona prevention in MMICs are desired.